Twenty seconds is about as long as singing Happy Birthday twice, and will help prevent nasty tummy upsets, the Royal Pharmaceutical Society said

The new advice comes after the National Institute for Health and Care Excellence (Nice) said people should aim for at least ten seconds after using the toilet and before preparing food.

RPS president Ash Soni said: “We don’t wash our hands often enough for long enough to get rid of the bacteria that can cause illnesses.

“Even when we remain unaffected by the bugs we carry, if we don’t wash our hands we can transmit infections which then become a real problem for those who are more vulnerable, such as children and the elderly, who may then need to be prescribed antibiotics.

“If we can reduce the number of illnesses where antibiotics are needed, we can reduce antibiotic resistance by saving these important medicines for when they are really required.

The RPS is calling for people to wash their hands more thoroughly to cut down on the need for antibiotics, which are becoming increasingly resistant to bacteria

“Antibiotics should not be given for viral infections but often still are, partly due to patient demand.

“It’s easy to pick up an infection and once ill, people often visit their GP to request antibiotics because they think they are not getting better quickly enough, when in fact infections can be expected to last longer than you might think.”

According to the RPS, sore throats last seven to eight days on average, ear infections last eight days, colds 14 days and a cough for 21 days.

It says people should look up the handwashing technique recommended by the NHS, which lasts for 20 seconds and includes the back of the hands.

Earlier this year a study found antibacterial handwash is NO better than soap at killing germs.

Scientists in the US also found cold water leaves hands just as clean as hot water.